1. Field of the Invention
The present invention relates to method and apparatus by which a take-off device efficiently transfers a molded article from the mold of an injection-molding machine. More particularly, the present invention relates to method and apparatus by which a suction sleeve extension ensures that the take-off device efficiently and reliably extracts the molded article from the mold.
2. Related Art
It is well known in the art of injection molding to transfer molded articles from a mold to a take-off device using suction to draw the article being released from a core pin into a tube on the take-off device. The take-off device is usually attached to a robot arm that enters into the space between the mold halves when the mold is open.
FIG. 1A shows an example of a known device used to transfer parts from a mold to a take-off device. A single take-off tube 74 mounted on a take-off plate 72 in a manner known in the art. In this FIG. 1A, a molded part 50 has been fully transferred into cooling tube 74 and ejector rail 14 is fully retracted. When part 50 is sufficiently cooled, rail 14 is moved upwardly in the drawing to engage a lip 52 of part 50 and discharge it from the tube 74 in a manner that is well understood in the art. A plug 8 is placed at the bottom of tube 74 and bolted to take-off plate 72. A port 10 in plug 8 provides a suction source to the tube 74 to draw parts into the tube 74. Cooling channel 12 provides coolant to the tube 74 to cool part 50 while in the tube 74. A sleeve 16 surrounds the tube 74 to confine the coolant in the cooling channel 12 in a manner that is well known in the art. However, in certain circumstances, the articles may not transfer properly using the presently known suction transfer devices.
Referring first to FIG. 1, a known take-off device 62 transfers molded articles 50 (which are being removed from core pins 38 by neck rings 98) by providing suction through ports 10 to the tubes 74. In certain circumstances, however, the articles 50 may not transfer properly. For example, if the molded article is of an irregular shape the suction provided in the tube 74 may be insufficient to draw the molded article into the tube 74 because of loss of suction between the core pins 38 and the tubes 74 due to the irregular shape of the molded article. In other circumstances, it may not be possible to bring the take-off device 62 into close proximity to the core pins 38 because of the need to maintain adequate clearance between the mold half 20 and the take-off device 62. In this situation, the transferring part 50 may drop out of alignment with the tube 74 and either jam against an edge of the take-off device 62 or even fall out of the mold half 20. Not only may the part be lost or malformed, the entire machine may be jammed, necessitating costly shut-downs and repairs.
FIG. 2 helps to illustrate these potential problems. The part 50 is formed on mold core 38. Neck ring 98 mounted on slide 96 cooperates with mold core 38 to form the neck portion of part 50. Slide 96 and neck ring 98 slide forward towards take-off device 62 to remove part 50 from mold core 38. As the neck ring 98 moves forward it separates to release the part 50. Neck ring 98 is shown in its open position where it is releasing part 50 so that it may be received by take-off tube 74. At this point, the distance between tube 74 and the releasing position of the neck ring 98 is significant with respect to the length of part 50. If there is a problem releasing the part 50 from the neck ring 98, the part 50 may not properly align with the tube 74 and either fall out of the mold or jam against the take-off device 62. The suction provided by the channel 10 may be insufficient to overcome this alignment problem because of significant losses in the space between the core 38 and the take-off device 62.
With the known take-off devices 62 shown in FIGS. 1, 1A and 2, there is nothing to prevent loss of suction in the space between the core pins 38 and the end of the tubes 74. When the tubes 74 and the core pins 38 cannot be brought into close proximity, or if the part 50 has an irregularly shaped outer surface, there may be insufficient suction and thereby cause the molded articles to transfer improperly.
Several patents teach other examples of devices used to transfer parts from a mold to a take-off device. U.S. Pat. No. 4,364,895 to Underwood discloses a mechanical ejection device that includes an air cylinder for providing air to the base of the article being ejected so as to minimize distortion of the article while it is being ejected from the mold.
U.S. Pat. No. 4,660,801 to Schad, assigned to the present assignee, discloses a mechanism for ejecting a cup-shaped work piece from a core. A core sleeve on the core is moved forward by fluid pressure to initiate release of the work piece from the core. As the core sleeve moves forward, it opens a fluid channel through the side of the core. Fluid through this side channel impinges on an inner surface of the work piece and assists in the removal of the work piece from the core.
U.S. Pat. No. 5,447,426 to Gessner et al., assigned to the present assignee, discloses a take-off device including an ejector.
U.S. Pat. No. 5,948,341 to Diamond et al., assigned to the present assignee, discloses apparatus for removing parts from a mold using a tool plate and pressurized air to move the part from the mold onto a retention apparatus.
U.S. Pat. No. 6,123,538 to Kutalowski, assigned to the present assignee, discloses a cooling device for a take-off device.
U.S. Pat. No. 6,391,244 to Chen uses a blocking portion on a take-off plate to prevent ejection of the preforms from the cooling tubes until the preforms have been partially separated from the cooling tubes.
However, nothing in the teachings above will ensure an efficient, reliable, and rapid transfer of parts from a mold to a take-off device.